SNMP Reference Guide

Management Information Base Object Identifiers

Each data class within a Management Information Base (MIB) is defined by an Object Identifier (OID).

OIDs are unique across all MIBs. An OID consists of a series of digits separated by periods. The OID

functions in a similar fashion to a phone number. The phone number 011-512-471-0000 uniquely

identifies a single phone. The phone number can be broken down into a number of components to

uniquely identify a phone. The first component, 011, is the country code for the United States. The

second component, 512, identifies the area code for central Texas. The third component, 471, is the

phone exchange for a large state university in the city of Austin. The final component, 0000, is the main

switchboard.

There are two main differences between the phone number example and an actual OID. The first

difference is that there are many more components in an OID, up to 128. The combination of these

components is called an OID prefix. The second difference is that OIDs support the concept of indexes or

keys. The OID prefix specifies the data class but does not specify an instance of the data within the class.

Indexes can be used to identify the instances of a data class. These indexes are referred to as the OID

suffix.

The assignment of values for each OID prefix component can be illustrated by using a tree structure. The

following is an example of an OID assignment:

Table 14. ROOT

CCITT(0)

ISO(1)

ORG(3)

DOD(6)

INTERNET(1)

MGMT(2)

MIB(1)

EXPERIMENT

AL(3)

PRIVATE(4)

ENTERPRISE

S(1)

DELL (674)

SNMPv2(6)

In the preceding example, the OID prefix for the Dell enterprise would be 1.3.6.1.4.1.674.

The numbers in boldface type show the categories and numbers that apply to Server Administrator. All

Server Administrator-defined OIDs consist of 1.3.6.1.4.1.674 followed by additional component values.

SNMP Security

SNMP version 1 has a very limited security mechanism. SNMP agents support the use of a community

string, which is configured at each SNMP agent and is passed as a part of all SNMP request messages.

There is no verification that the requester is actually a member of the specified community. As most